1. Field of the Invention
The present invention relates to a solenoid-operated valve having the durability improved by reducing sliding resistance of a movable iron core when a solenoid is excited to displace the movable iron core.
2. Description of the Related Art
A solenoid-operated valve has been used to supply a pressure fluid to an actuator or discharge a compressed air to an atmospheric air so that a flow direction of the compressed air may be controlled. Generally, the solenoid-operated valve has a valve plug operated by a solenoid (electromagnet).
As shown in FIG. 6, a conventional solenoid-operated valve of the above type comprises a coil housing 5 and a valve body 9. The coil housing 5 houses therein a fixed iron core 1, a coil 2, a movable iron core (plunger) 3, a magnetic plate 4 or the like. The valve body 9 includes a diaphragm 8 for opening/closing a valve seat 7. A pair of fluid inlet/outlet ports 6a, 6b are communicated with each other by the valve seat 7 (see Japanese Laid-Open Patent Publication No. 3-61776).
A clearance E (air gap) is formed between the outer circumferential surface of the movable iron core 3 and the inner circumferential surface of the annular magnetic plate 4. An attracting force of the magnetic plate 4 attracts the movable iron core 3 radially outwardly.
It is a general object of the present invention to provide a solenoid-operated valve which reduces sliding resistance of a movable iron core to a sleeve when the movable iron core is displaced, thereby enabling the movable iron core to slide more smoothly without lowering a force of a solenoid for attracting the movable iron core.
A principal object of the present invention is to provide a solenoid-operated valve which prevents dust or the like from being generated at a sliding portion of a movable iron core.
The above and other objects, features, and advantages of the, present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative, example.